Hydro-pneumatic energy storage device



July 7, 1959 s. l. MaGDUFF HYDRO-PNEUMAT1C ENERGY STORAGE DEVICE Filed June 6, 1956 INVENTOR. SEQ/LEY' MFDU/:f

A TTORNE K United States .Patet 2,893,433 Patented July 7, 1959 .rice

HYDRO-PNEUMATIC ENERGY STORAGE DEVICE Stanley I. MacDul, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application June 6, 1956, Serial No. 589,616

3 Claims. (Cl. 138-30) This invention relates to hydro-pneumatic energy storage devices of the bladder type, and more specifically to an improved sealing means provided at the open end of the bladder.

In general, accumulators comprise a shell or a plurality of shells having a gas chamber and a hydraulic chamber with a iiexible partition therebetween, so that the hydraulic fluid will not be contaminated by having the gas dissolve in it. The hydraulic uid is under pressure from a pump and acts against compressed air or other gas which has been placed in the gas chamber. The compressed gas exerts a steady pressure on the liquid -but is compressible so that varying quantities of liquid may be stored in the accumulator. Since accumulators have a high internal pressure, it is important to use a truly spherical form for the accumulator especially where light weight is desirable because the stability of the spherical form permits the use of relatively thin gauge material for the shell or shells. With such a stable form, the only stresses which must be withstood are simple bursting stresses occasioned by the internal pressure.

Accumulators of the general type to which this invention relates may be used in automotive or aircraft hydraulic systems where many devices are operated from fluid under pressure from one pump. In these systems a power driven pump is continuously operated, but since the many devices may be operated intermittently. the required liquid may be less or greater than the output of the pump. When the liquid demand is less than the pump output, liquid is stored under pressure in the accumulator, and when the accumulator is filled, the pump output is bypassed to the reservoir. When the liquid demand exceeds the capacity of the pump, the accumulator supplies the necessary liquid under pressure. Thus one purpose of an accumulator is to permit the use of a small pump for a hydraulic system with momentary demands in excess of the capacity of the pump.

Accumulators which are constructed of a plurality of shells which grip or provide means for gripping a bladder at the junction of the shells often are inefficient because of air and/or oil leakage at this point.

It is therefore an object of this invention to provide a sealing arrangement at the open end of the bladder which will be effective to prevent the respective media contained on the opposite sides of the bladder from leaking therearound either into contact with each other or from leaking to the surrounding atmosphere.

The above and other objects and features of the invention will be apparent from the following description of the apparatus taken in connection with the accompanying drawings which form a part of this specification, and in which:

`Figure 1 is a vertical section of the accumulator incorporating a bladder in accordance with the invention; and

lFigure 2 is an enlarged fragmentary section of the open end of a bladder showing serrations formed thereon.

Referring to Figures 1 and 2 of the drawings the numeral 10 designates :an accumulator which has a lower shell 12 and an upper shell 14. The lower shell 12 has a spherically rounded portion 16, a -cylindrical portion 18 which surrounds the spherical portion, and a generally rounded fold 20 which connects the two portions. The upper shell 14 has a hemispherical portion 22 and a cylindrical portion 24 extending from the hemispherical portion which envelops the cylindrical portion 18 of the lower shell 12 in such a manner that the cylindrical portions of each shell will be contiguous. A supporting member 26 having a substantially cylindrical shape is placed between the rounded and cylindrical portions of the lower shell for reinforcement. The upper and lower shells and the supporting member are connected together by `a. weld 28. The lower shell 12 has a pneumatic opening 30 and the upper shell 14 has an opening 32 for passage of hydraulic fluid. A hydraulic fitting 34 is welded or otherwise securely attached to the upper shell at 36.

A bladder 38 which is molded open on one end is disposed within the upper shell 14 and is secured therein by a retainer 40 to form a pneumatic chamber 42 with said retainer. A hydraulic chamber 43 is formed between the bladder 38 and the upper shell 14. The retainer has a spherically rounded portion 44 which is contiguous with the spherically rounded portion 16 of the lower shell 12 and a substantially cylindrical extension 46 the end of which is rolled over to provide a `bead 48. The cylindrical extension 46 and bead 48 of the retainer secure the end of the bladder at the junction Sil of the lower and upper shells. A pneumatic valve 52 is welded to the retainer 40 at 54 and passes through opening 30 of the lower shell 12. The outer portion of the valve is threaded so that a nut 56 can hold the retainer 40 tightly against the lower shell.

The bladder 38 is preferably provided with a substantially rigid or stationary portion 58 which is formed to t snugly against the cylindrical portion 24 of the upper shell from the junction 5t) to substantially the equatorial line 60 of the accumulator and a flexible portion 62 which extends from the equatorial line to the closed end of the bladder and is 4adapted to fold into the stationary portion 58 to a lesser or greater extent when hydraulic fluid enters the hydraulic chamber 43 and compresses the gas within the bladder. lf the gas becomes completely eX- hausted from within the bladder for any reason and hydraulic uid enters the opening 32, the llexible portion 62 will be completely telescoped into the stationary portion 58 and will fold about the equatorial line 60 due to the increased thickness of the stationary portion.

In order to prevent the trapping of hydraulic fluid between the bladder and the upper shell, small buttons or bosses 64 are provided on the exterior surface of the flexible portion 62 of the bladder. The bosses 64 on the bladder contact the upper shell iirst and maintain the outer surface of the bladder' intermediate the bosses in spaced relation with respect to the shell, so that any fluid trapped between the bladder and the shell at a point spaced away from the hydraulic opening 32 can still flow between the bosses 64 to the opening 32.

The closed end of the bladder is reinforced with a rigid bladder button 66 to prevent the extrusion of the flexible bladder wall into the hydraulic opening 32 in case of hyhydraulic pressure failure. A porous metal insert 68 is placed within the gas opening to prevent the extrusion of the bladder in the event of gas loss. This type of metal will form an impervious wall to material such as synthetic rubber but will not prevent gas from passing freely therethrough.

The flexible portion 62 of the bladder preferably has a relatively flat end spaced from the end of the upper shell when the bladder is in an unstressed position, sinceit has been found that this construction tends to promote the orderly collapse and distension of the bladder during operation.

In order to prevent leakage between the hydraulic and pneumatic media or of either to the atmosphere, the open end of the bladder is provided with serrations 'it and 72 on both sides of the bladder. The cylindrical extension 46 and the cylindrical bead 4S of the retainer 4@ secure the end of the bladder along the serrations 70 and 72 in conjunction with the lower and upper shells 12 and 14. By adding the serrations to the open end, greater resilience is achieved over the contact `area and an improved seal will result. This seal is achieved by constructing the upper shell 14 and retainer 40 so that there will be an interference across the serrated end. Also, the bead 4% provides longitudinal compression due to the nut 56 which holds the retainer 40 tightly against the lower shell 12.

By providing such an improved seal, air and oil are prevented from leaking out of their respective chambers between the retainer 4G and lower shell 12 or between the cylindrical portions 18 and 24 of the upper and lower shells to the atmosphere.

The several practical advantages which ow from the sealing means employed'in this hydrospneumatic energy storing device are believed to be obvious from the above, and other advantages may suggest themselves to those who are familiar with the art to which this invention relates.

Having thus described the various features of the invention, what 1 claim as new and desire to Vsecure by Letters Patent is:

1. A hydro-pneumatic energy storing device comprising a first shell having an opening for passage of cornpressed gas, a second shell having an opening for passage of hydraulic fluid, said first shell having a spherically rounded portion and a cylindrical portion, said cylindrical portion surrounding said rounded portion, a hemispherical second shell having a cylindrical portion extending therefrom, said cylindrical portion of the second shell encircling the first shell so that the cylindrical portion of each shell will be contiguous, a supporting member between the spherically rounded portion and the cylindrical portion of the first shell for reinforcing said first shell, means for connecting the supporting member and the cylindrical portions of said shells to each other, an open ended bladder disposed within said second shell to form a hydraulic chamber with said second shell, serrations formed on the inner and outer surfaces of said bladder at the open end, a retainer having a spherically rounded portion contiguous with said first shell and a substantially cylindrical extension with a bead formed thereon, said cylindrical portion and bead of said retainer securing the bladder along said serrations in conjunction with said first and second shells thereby providing a pneumatic chamber formed by said retainer and said bladder, and a pneumatic valve connected to said retainer.

2. A hydro-pneumatic energy storing device comprising a spherically rounded first shell, a spherically rounded second shell, and a spherically rounded retainer disposed within and contiguous with said rst shell, a bladder disposed within said second shell and having a substantially rigid first portion formed to fit against said second shell and a exible portion adapted to telescope into the first portion when the bladder is collapsed, said bladder being confined at the junction of said rst and second shells by said retainer, said first portion having serrations formed thereon for preventing the escape of the hydro-pneumatic media as a result of leakage between said shells and said retainer.

3. A hydro-pneumatic energy storing device comprising two contacting shells, a retainer disposed therein, a bladder having a substantially rigid first portion formed to fit against `one of said shells and a flexible portion adapted to telescope into the first portion when the bladder is collapsed, said bladder being confined along the rst portion at the junction of said two shells by said retainer, said first portion having ridges formed thereon for preventing the escape of the hydro-pneumatic media as a result of leakage between said shells and said retainer.

References Cited in the le of this patent UNITED STATES PATENTS 2,216,374 Martin Oct. l, 1940 2,339,076 Huber ian. 1l, 1944 2,378,467 De Kiss June 19, 1945 2,397,248 De Kiss Mar. 26, 1946 2,740,259 Westlund Apr. 3, 1956 2,757,689 Knox Aug. 7, 1956 

